1. The Last 10,000 Years of Human History
By 1810, population ~1 billion
By 1925, population ~2 billion
By 1960, population ~3 billion
By 1974, population ~4 billion
By 1987, population ~5 billion
By 1999, population ~6 billion
By 2017, population ~7.6 billion
The present human population of the world is a little more than ______________. 
In the last 50 years of the 20th Century, world population grew from ______ billion to over 6 billion.

2. The Human Population Today
Growth rate = (birth rate) – (death rate)
Human population grows by about 70 million people per year
Present population of the world id 7.6 Billion
The growth rate is 1.1% per year
Doubling time = 200 years (In 2217 it will be 15.2)
The growth rate of the world population equals ________________.

3. MATHS: Future World Population
BUT the world’s population explosion continues
From 1950 to 2000 population grew from 2.5bn to 6bn
Growth rate of 1.3% per year means 9 billion by 2050
We need the number of births per woman to predict 2050 population (you will be 47 and a grandparent maybe)
If...average 1.6 children/woman: 3.6bn
If...average 2 children/woman: 10.8bn
If...average 2.6 children/woman (current average): 27bn
At present, after subtracting deaths from births, world population increases 1.3 percent per year for a doubling time of __________________.
At present, the world population of humans grows by over ______ million per year. 

4. Future World Population

5. What about? Too many people? Crowding in cities Crime Pollution
Illegal migration
Disease
Room for more people?
Entire world population could fit inside 42 km x 42 km square
Consider carrying capacity

6. Carrying Capacity How many people can Earth support?
Calculations of carrying capacity vary considerably
Increasing amounts of food can be produced
People can migrate from areas of famine or poverty to less crowded or wealthier areas
BUT Earth’s resources are finite, so solutions are temporary

7. Carrying Capacity Example of Rapa Nui (Easter Island)
Isolated Pacific island with poor soil and little water
Settled by people from polynesia 400AD
Survived easily on chickens and yams, plenty of free time
Developed elaborate competition between clans with
Civilization peaked at 1650, with population of about 10,000

8. Carrying Capacity Example of Rapa Nui (Easter Island)
Reached by a Dutch ship in 1722
Found 2,000 people living in caves
Primitive society and at war with each other.
Rapa Nui’s carrying capacity had been drastically lowered by society’s actions:
Transportation of moai had required cutting down trees
Erosion of soil made yams scarce
Lack of canoes made fishing difficult and escape impossible